The proposed study arises from the need to develop effective treatment for women with comorbid posttraumatic stress disorder (PTSD) and substance use disorder (SUD). Women with PTSD are estimated to comprise 29% to 39% of SUD treatment samples, and are documented to show a more severe course than women with wither disorder alone. As yet, no effective treatment for this substantial population has been identified. To attend to this problem, the applicant has developed a treatment manual explicating a new, cognitive behavioral group therapy specifically adapted to their clinical needs as part of a Stage 1 treatment project of the NIDA Behavioral Therapies Development Program. This 24-session, highly structured program offers an intensive rehearsal of cognitive behavioral, and interpersonal coping skills, using techniques empirically validated in the educational literature to make the treatment accessible and engaging for this population. It is cost-sensitive (i.e., a group format), has been revised on the basis of actual experience and empirical results of its impact, and targets topics believed most central for such women (e.g., HIV risk). Its primary goal is abstinence from all substances. Initial empirical results of its impact, based on 17 patients, show statistically significant and clinically meaningful improvements in several areas: (a) in substance use as early as one month into treatment and lasting through a 3-month follow- up, (b) in PTSD symptoms; and (c) in the domain most theoretically relevant to the treatment, cognitions. Attendance was high (67% of available sessions), and ratings of alliance and satisfaction with the treatment were very strong. The proposed study is designed to take this promising treatment to the next logical level of Stage 1 evaluation that is, against a "treatment-as-usual" control group. To maximize the usefulness of such as control group in testing the effects of the CB treatment, all patients will be restricted in the amount and types of treatments they may attend while participating in this study. The target sample is 25 patients each in the treatment and control conditions. The study will: (a) estimate the effect size of the treatment compared to the control, using reduction in substance use as the primary outcome measure; (b) test the manual using expected "consumers of it (four therapists independent of the investigators); (c) evaluate patients monthly through a 9-month post-treatment follow-up period to assess maintenance of gains; and (d) psychometrically validate two new instruments that are theoretically derived from this treatment (a therapist adherence scale, and a patient "core components of treatment" scale that attempts to measure hypothesize mechanisms of action of the treatment).